The present invention relates to a load-shifting device having a control element which acts on a setting member, wherein the setting member determines the power output of an internal combustion engine, and the control element cooperates with a driver. The driver is coupled with an accelerator and, in addition, can be controlled by an electric setting drive which cooperates with an electronic controller.
Load-shifting devices, for instance load-shifting devices cooperating with carburetors or injection pumps, must satisfy the need for optimum control of the internal combustion engine over its entire load range. This requires a complicated construction or a complicated control of the load-shifting device. Thus, carburetors, for example, have, in addition to the actual device for the forming of the mixture, additional devices such as thinning, starting, idling, accelerating, economizing devices, etc. These devices complicate the construction of the carburetor and result in increased expense for parts since, for example, additional injection nozzles, pumps, special developments of nozzle needles and separate air feeds are required, entirely aside from extracting control requirements inherent in this.
Of particular importance in the case of load-shifting devices is the control of the load condition under idling. During idling, only minimal power is given off by the internal combustion engines, however, there may be present, especially in the case of automobiles, load consuming devices which require a high power output, such as fans, rear-window heating, air conditioners, etc. In order to take these potential demands on the power into account, control of the load-shifting device between a maximum and a minimum idling setting is required. Also upon failure of the control, an idle emergency setting of the setting member or of the control element must be assured.
Differing from the problem described above, load-shifting devices of the aforementioned type are, as a general rule, used in cases where the accelerator and the setting member are electronically connected to each other. The accelerator is coupled to the driving device and the latter is connected to the control element. Furthermore, a desired-value detection element associated with the driver and an actual-value detection element cooperating with the desired-value detection element and acting on the electric setting drive are provided. The electric setting drive is controllable by the electronic controller as a function of the values detected.
The electrical connection of accelerator and setting member with the interposed electronic controller makes it possible, by means of the accelerator and the driver coupled thereto, to compare predetermined desired-value positions with the actual-values indicated by the position of the control element and the setting member. These elements can also be checked for the presence or absence of plausibility conditions. Thereby, upon the presence or absence of given plausibility conditions, there is the possibility of exerting a correcting action, via the electronic controller, by controlling the electric setting drive, on the setting member. The setting member may formed as a throttle valve or injection pump. Thus, action by the electronic controller for the avoidance of wheel slippage of an automotive vehicle, upon starting due to an excessive power output called for by the accelerator, can be provided. Other automatic interventions into the load-shifting device are to be considered in the case of automatic shifting processes of a transmission or a speed-limiting control.